A CANADAIR CL65 IN CRUISE AT FL280 DECLARED AN EMERGENCY AND DIVERTED DUE TO AUXILIARY PWR UNIT FIRE WARNING; ENG OVERHEAT WARNING AND LEFT ENG FIRE WARNING CAUSED BY A FAILED FIRE AND OVERHEAT CTLR.

Narrative

AT FL280 CRUISE ALTITUDE AN APU FIRE WARNING MESSAGE WAS ANNUNCIATED. QRH PROCEDURES WERE INITIATED. NEXT; A JET PIPE OVERHEAT WARNING MESSAGE WAS ANNUNCIATED. QRH PROCEDURES WERE INITIATED AND THE MESSAGE WENT OUT. AN EMERGENCY WAS DECLARED AND WE PROCEEDED TO THE NEAREST ARPT TYS. NEXT; A LEFT ENG FIRE WARNING MESSAGE WAS ANNUNCIATED. QRH PROCEDURES WERE INITIATED WHICH LED TO A SHUTDOWN OF THE LEFT ENG. THE SQUIBS WERE BOTH DISCHARGED AND THE MESSAGE PERSISTED. THE FLIGHT ATTENDANT AND PASSENGERS WERE BRIEFED. A LNDG AT TYS RESULTED IN AN ORDERLY EVACUATION ON THE RWY THROUGH THE MAIN CABIN DOOR. NO INJURIES OR ACFT DAMAGE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT AT FIRST THE APU FIRE WARNING WAS ANNUNCIATED AND THE APU WAS SECURED PER THE QRH. THE RPTR SAID THE JET PIPE OVERHEAT CAME ON AND WAS HANDLED PER THE QRH AND THEN THE LEFT ENG FIRE WARNING CAME ON. THE RPTR STATED THE ENG WAS SHUT DOWNN AND THE FIRE BOTTLES DISCHARGED. THE ACFT WAS EVACUATED ON THE RWY. THE RPTR SAID MAINT DISCOVERED A FAILED OVERHEAT AND FIRE WARNING CTLR WHICH CONTROLS ALL OVERHEAT AND FIRE WARNING LOOPS AND SENSOR INPUTS. THE RPTR SAID THIS BOX SHOULD BE BROKEN DOWN INTO THREE SEPARATE UNITS TO AVOID MULTIPLE WARNINGS THAT OCCURRED IN THIS INCIDENT.